Feasibility and efficacy of carotid-cavernous fistulas embolization with Onyx combined with coils: a systematic review and single-arm meta-analysis

Introduction Carotid-cavernous fistulas (CCFs) are abnormal arteriovenous shunts between the carotid system and cavernous sinus, often managed through endovascular embolization. While both Onyx and coils are used independently, their combined use lacks consolidated data. This review aims to assess the feasibility, angiographic efficacy, and clinical outcomes of Onyx combined with coils in the treatment of CCFs.Methods A systematic review and single-arm meta-analysis were conducted following PRISMA guidelines. Six observational studies comprising 101 patients with CCFs treated with combined Onyx and coil embolization were included. Primary outcomes were initial and follow-up complete angiographic obliteration rates. Secondary outcomes included clinical improvement and no clinical improvement or deterioration. Pooled proportions with 95% confidence intervals (CIs) were calculated using a random-effects model.Results The pooled initial complete obliteration rate was 90% (95% CI: 78–95%), increasing to 94% (95% CI: 90–96%) at follow-up. The initial partial obliteration rate was 10% (95% CI: 5–22%), which decreased to 5% (95% CI: 3–10%) by the last follow-up. Clinical improvement was observed in 95% (95% CI: 90–97%) of patients. The rate of no clinical improvement or deterioration was 5% (95% CI: 3–10%). All analyses demonstrated low heterogeneity (I2 = 0%), indicating consistent results across studies.Conclusion Embolization of CCFs using Onyx combined with coils is a highly effective and safe treatment, yielding consistently high obliteration and symptomatic resolution rates. This approach appears especially promising for direct (type A) fistulas. Nevertheless, larger prospective studies are needed to establish its comparative efficacy across all CCF subtypes.